The Hyphen [and the Dash] | Guide to Grammar and Writing, Capital Community College

I'm amused occasionally when I hear people talking about using a dash in their writing. It sometimes seems like dash is the only name for a punctuation mark that's a single horizontal line in the middle of a character space.

Of course, it's not. The hyphen also meets that description. And there are two forms of a dash. 

The Web article at Capital Community College covers some uses of the hyphen and notes several other references (the Chicago Manual of Style and two bad links). So, if you don't have the excellent Chicago Manual handy, here's advice from Garbl's Editorial Style Manual for both the hyphen and the dash.

hyphen (-) Hyphens are joiners. They link words. Use a hyphen to avoid ambiguity or to form a single idea from two or more words: His boss recovered her health. Her son re-covered the torn seat. He is a small-business man. She is a foreign-car dealer. Unclear: He is a small businessman. She is a foreign car dealer. [My online style manual also provides related guidelines at the entries for composition titles, compound words, initial-based terms, and race.]

Don't hyphenate most compound nouns--two or more words that work together as a noun: Agent training is running late. But consult this style manual or your dictionary for preferred or commonly excepted terms: president-elect, sister-in-law, good-for-nothing.

Compound adjectives, compound modifiers:

• To avoid ambiguity, use hyphens to link words in compound adjectives (compound modifiers) before nouns. The words in compound adjectives work together to describe the noun. If you can insert and between the modifying words before a noun and make sense of the new construction, you do not have a compound adjective: And would make sense in a sunny, warm day; sunny, warm is not a compound modifier. But and would not work in a well-rounded employee; well-rounded is a compound modifier. Another test: If your sentence would make sense if you reversed the order of the modifying words or even removed one of them, don't connect the words with a hyphen.
• Here are other examples of two or more consecutive words that make sense only when linked with a hyphen as a single idea modifying a noun that follows: better-qualified woman, credit-card application, first-class stamp, 5-ton truck, high-frequency sounds, know-it-all attitude, little-known man, long-range plan, minimum-height requirement, minimum-height requirement, pilot-testing schedule, short-term solution, special-interest money, 250-square-mile area, two-zone system, used-record store, a well-prepared plan.
• Leave out hyphens in compound modifiers only when no reader confusion would result from their omission--or if the modifying words are commonly considered as a unit: post office box, high school classes, real-estate agent. Also, rewrite sentences to avoid stringing together a long, potentially confusing series of modifying adverbs and adjectives before nouns.
• When a number and a noun form a compound modifier before a noun, use a singular noun in the phrase and hyphenate the phrase. Drop the hyphens and use plural nouns in other uses: The room measured 6 by 9 feet, but a 6-by-9-foot room. The building has 3,300 square feet of usable space, but a 3,300-square-foot building. The container held 10 gallons, but a 10-gallon container. The type size is 18 points, but 18-point type. Her shift lasted 10 hours, but a 10-hour shift. She was on vacation for three weeks, but a three-week vacation.
• Hyphens are unnecessary after already, least, less, most and very and after all adverbs that end in ly: already named manager, an easily remembered rule, less expensive project, least liked alternative, most used service, randomly selected addresses, a very good time. ...
• Don't hyphenate most compound modifiers if they occur after the noun being modified, even if hyphenating them before the noun: The proposal was well documented. The actor was little known. The older woman was better qualified. His boat is 42 feet long, but He has a 42-foot-long boat.
• Here's the form for suspensive hyphenation: The students recommended a 15- to 20-minute break between third and fourth periods.

Hyphenate co- when forming nouns, adjectives or verbs that show occupation or status: co-chairman, co-pilot, co-worker. [The prefixes and suffixes in my online style manual -- and separate entries for the most often used prefixes and suffixes -- also provide advice on using hyphens.]

A hyphen is not a dash. For example, this organization mail stop, KCS-NR-0505, has hyphens, not dashes. And this phone number has hyphens, no dashes: 206-456-7890. See dash [below] for preferred punctuation between phrases and numbers, times, dates and other uses that show range, such as 1993-94, $23-42, the Seattle-Spokane train. Also see between ..., from ... to, ranges.

A hyphen may be used to divide a word at the end of a line, especially to remove large gaps at the end of an adjacent line. Here are some guidelines for hyphenation to aid readability and reduce reader confusion:

• Divide words only between syllables, but don't add a hyphen to a word or phrase that already has a hyphen, such as decision-maker or re-election. Instead, break the word or phrase at the existing hyphen.
• Avoid ending more than two consecutive lines with hyphens.
• Don't hyphenate a word at the end of a line unless you can leave a syllable of at least three characters on both the first and second lines. Avoid dividing words with fewer than six letters.
• Don't divide the last word in a line when the second part of the word would be the only "word" on the second line.
• Don't hyphenate abbreviations, contractions and numbers. Also, don't hyphenate words in headlines and headings.
• Avoid hyphenating proper nouns.
• Don't hyphenate words that jump from one page to another page.
• Avoid hyphenating words that jump from one column to another column or that jump over a graphic image or photo.

dash (--) Long dashes, called em dashes, have three main uses. In these uses, em dashes are usually less formal but more emphatic substitutes for other typical punctuation marks. To preserve the impact of dashes, avoid overusing them. [A note at the end describes how to form dashes; two hyphens next to each another, as shown above, is one way.]

First, use an em dash to explain, justify or stress in the second part of a sentence something in the first part: Fans filled all the seats--the concert hall was packed! The new shopping mall will open Tuesday--if the air-conditioning works. The project was finished on time, within scope--and under budget. The manager was new to the agency--brand new.

Second, use a pair of em dashes to make an emphatic pause or abrupt, parenthetic change in thought within a sentence: The new auditorium--opening six months behind schedule--is getting praise from both critics and audiences. If you'd prefer to play down such a phrase, consider placing it between parentheses instead, or between commas.

Third, use a pair of em dashes to set off a phrase that has a series of words separated by commas: Leif Nelson described the qualities--intelligence, a sense of humor and compassion--he wants in a manager.

As shown in the examples above, do not put a space before or after an em dash (an exception to the rule followed by the Associated Press for newspaper use). 

Avoid using more than one pair of em dashes in a sentence.

A short dash, called en dash, may be used to mean up to and including when placed between numbers, times, dates and other uses that show range: 1993-96, $25-50, $432,000-$560,000 (but $25 million to $50 million), 55-65 years, 7:15-7:30 a.m. (but 9 a.m. to 3:30 p.m.), ages 15-20, pages 167-78. It also may be used to replace to and versus in capitalized names: the Chicago-New Orleans train, the Huskies-Cougars game. Do not put spaces before and after the en dash. See between ... and, from ... to, dates, ranges [in my online editorial style manual].

Note: A hyphen (-) is not a dash. Most current word processing and design software can create em dashes and en dashes. If not possible, use two hyphens to create an em dash, and substitute a hyphen for an en dash. In Microsoft Word, if you don't space after the second hyphen, the two hyphens become an em dash. See hyphen.